1. Field of the Invention
The present invention relates to Refrigeration, and specifically to reducing costs, by increasing the effectiveness of Surroundings Heat Exchangers and by more efficiently recovering reject heat for water heating.
2. Prior Art
Refrigeration Systems are used for maintaining the contents of enclosed spaces, which are separated from their surroundings by the enclosing walls, at depressed or elevated temperatures. In some cases the functions of refrigeration and heat pumping are combined to keep the contents of one or more enclosed spaces at depressed temperatures while also keeping the contents of one or more other enclosed spaces at elevated temperatures. The objective is frequently to delay deterioration of the contents of the enclosed space, to maintain enclosed spaces at comfortable temperatures for occupation by humans or other animals, or to adjust the temperature of materials in preparation for use. In the past said contents of said enclosed spaces have been maintained, at the desired temperatures, using Surroundings Heat Exchangers, maintained at temperatures greater (in the case of refrigeration systems) and less (in the case of heat pumping systems) than those of the surroundings immersed in the surroundings, which exchange heat with said surroundings. Said heat transfer is required to counteract heat which is transferred (by conduction, convection or radiation) through the enclosing walls, which are normally insulated, in addition to heat transferred along with material exchanged between the surrounding space and the enclosed space and heat generated or absorbed within the enclosed space (e.g. by chemical reaction or electric heater). Frequently the surroundings comprise gasses, such as air, and said heat is frequently exchanged between the Surroundings Heat Exchangers and said gasses. The heat transfer coefficients between solid heat exchange surfaces, and gasses are very low, as is well known to workers in the heat transfer field. Since the heat flow rate is approximately proportional to the product of said coefficient, the heat exchange area, and the temperature differential, it is necessary to maintain a large temperature differential in order to drive the heat exchange between Surroundings Heat Exchangers and gaseous surroundings. The alternative of providing large heat transfer surfaces is limited by cost and available space. The maintenance of said large temperature differentials, for heat transfer, results in large differences between the temperatures of the Heat Supplier and the Heat Absorber of the Refrigeration System. As is well known to workers in the field of refrigeration, the efficiency of Refrigeration Systems increase as said temperature differences decrease. Consequently the maximum achievable efficiency of the Refrigeration System is adversely affected by the fact that the heat load must be transferred between said gas and said Surroundings Heat Exchanger. Typical residential refrigerators operate with heat supplier temperatures about 50.degree. F. above the temperature of the surroundings. Previous efforts to reduce the effect, of said low heat transfer coefficients, on efficiency, comprise those described in the "Prior Art" section of my application Ser. No. 08/030,734 filing date Mar. 6, 1993, as well as the Enclosure Heat Exchanger improvements disclosed in said application. Reject heat from residential type air conditioning is used for residential type water heating in commercially available equipment. This practice, although beneficial, is of limited value because the real time supply of waste reject heat from air conditioning systems is typically poorly correlated with the real time demand for heat for water heating. The use of reject heat from residential type refrigerators for residential type water heating, has been described in my application Ser. No. 08/030,734 filing date Mar. 6, 1993. The rationale for that invention includes improved efficiency, due partly to reduced temperature differences between heat supplier and absorber, substantially to the minimum temperature difference at which the insulated enclosure, the heat absorber or heat supplier, comprising given largely enveloping construction, could maintain a given space at a given temperature, within given surroundings at given temperature, in the absence of other heat absorber or heat supplier, (made possible by enveloping heat exchangers or avoidance of, notoriously poor, gas side heat transfer characteristics, or both), but other important factors comprise; the typical good match, in both quantity and temperature, between the reject heat available and the heat required for water heating; the typical proximity of the two appliances involved; and excellent real time correlation between supply and demand. Although the above referenced contributions have improved the performance of refrigeration systems, and in some cases have increased efficiency, or in other ways reduced operating costs, none of them have achieved or fulfilled the objectives of the present invention; one of which is to reduce operating costs, by reducing the temperature difference between the Surroundings Heat Exchanger and the Enclosure Heat Exchanger, by reducing the temperature differentials required for heat transfer, by use of Enveloping Surroundings Heat Exchangers; and the second of which is to improve the efficiency of water heating heat pumps by segregating the water either by the heat pump zone or by both the heat pump zone and the usage stream.